1. Field of the Invention
This disclosure relates to paperboard substrates having good oil and grease resistance, yet with full recyclability and without a tendency toward blocking.
2. Description of the Related Art
Oil and grease resistance is one of the top needs for paperboard packages in food and food service industries. Several technologies including specialty chemical (wax, fluorochemicals, starch, polyvinyl alcohol (PVOH), sodium alginate, etc.) treatment, polymer extrusion coating (polyethylene, etc.) have been employed to provide oil and grease resistance of paperboard packaging. However, the paper or paperboard treated with wax or coated with polyethylene, which is currently used in oil and grease resistant packaging, has difficulties in repulping and is not as easily recyclable as conventional paper or paperboard. Paper or paperboard treated with specialty chemicals such as fluorochemicals has potential health, safety and environmental concerns, and scientists have called for a stop to non-essential use of fluorochemicals in common consumer products including packaging materials.
Thus, there is still a critical need for oil and grease resistant paperboard that is 1) high performance, 2) without environmental or safety concerns, 3) recyclable, and 4) low cost. Aqueous coating is one of the promising solutions to achieve these goals. However, blocking (the tendency of layers in a roll of paperboard to stick to one another) is a challenging technical hurdle in production and converting processes for aqueous barrier coated paperboard, and blocking is also a major technical hurdle for on-machine application of aqueous barrier coatings. Furthermore, most aqueous barrier coatings are not fully repulpable. The current invention addresses the problems discussed above.